Simple method for preparing hydrogenated amorphous silicon films by chemical vapor deposition at atmospheric pressure
An inexpensive one-step method is presented for fabricating hydrogenated amorphous silicon (a-Si:H) films with good photovoltaic properties using chemical vapor deposition (CVD) from a mixture of silane, disilane, trisilane, and higher polysilanes in hydrogen at one atmosphere total pressure. The gas mixture is generated by the action of dilute acid on magnesium silicide and used immediately in the CVD process. Thus, elaborate techniques for handling, transporting or storing the pyrophoric polysilanes are avoided. In addition, the method requires no expensive vacuum or electrical equipment. The conditions necessary for high (approx. =10%) hydrogen incorporation and very high deposition rates (50-100 A/sec) are explained. Experimental parameters are explained and properties as a function of these parameters are shown. The measurements include hydrogen content, optical, electrical and photovoltaic properties of the a-Si:H films. A chemical kinetic model is presented for this and other silane and polysilane CVD systems between about 400 and 600/sup 0/C. Both homogeneous and heterogeneous reactions are considered. The model is derived from homogeneous gas-phase silane and polysilane chemistry and predicts, in agreement with our experiments, that the homogeneous gas-phase chemistry determines the a-Si:H film growth rate under a variety of conditions. The model is sufficiently predictive to be useful in determining appropriate experimental conditions. Stable solar cells are proposed for a-Si:H and fluorine doped tin oxide which can be produced by CVD at very high deposition rates. The unstable a-Si:H/tin oxide interface is eliminated by a very thin layer of titanium nitride and oxide between the a-Si:H and tin oxide.
- OSTI ID:
- 6629574
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
140501* -- Solar Energy Conversion-- Photovoltaic Conversion
36 MATERIALS SCIENCE
360601 -- Other Materials-- Preparation & Manufacture
CHEMICAL COATING
CHEMICAL VAPOR DEPOSITION
DEPOSITION
DIRECT ENERGY CONVERTERS
ELEMENTS
EQUIPMENT
FABRICATION
FILMS
HYDRIDES
HYDROGEN
HYDROGEN COMPOUNDS
NONMETALS
ORGANIC COMPOUNDS
ORGANIC SILICON COMPOUNDS
PHOTOELECTRIC CELLS
PHOTOVOLTAIC CELLS
SEMIMETALS
SILANES
SILICON
SILICON COMPOUNDS
SILICON SOLAR CELLS
SOLAR CELLS
SOLAR EQUIPMENT
SURFACE COATING
THIN FILMS